Changes in relative proportions of the components of elastin and collagen in normal aging will be determined. Elastic tissue from parenchyma such as lung contains a microfibrillar component, a glycoprotein, as well as amorphous elastin. The changing proportions are being established by morphological observations and by chemical analyses. In addition the microfibrillar component of lung elastin will be isolated, purified and characterized. Concurrently changes occur in the proportions of type I and III collagen. New approaches will be sought to establish the in vivo ratio of these collagen types in various age groups. It is also planned to compare the rates of change in elastin and in collagen composition and the age groups subject to maximum shifts. Finally possible qualitative changes associated with aging will be tested by analysis and by immunological cross reactivity of lung connective tissue components derived from different age groups.